Genetics in Dentistry

IN dentistry, numerous differences in the dentofacial characteristics of individuals are encountered, so that one is often moved to wonder whether oral health, as a condition, is inherited. Some members have a high prevalence of dental caries even within a family, while others may be caries-free. Such observations make it difficult to answer the question on the genetic basis of oral disease.

Regardless of abnormal or normal individual states, how do these differences come about? To deal with this question, it is necessary to turn to genetics. When we examine a specific characteristic or disease in the oral region, we often find it the consequence of two principal factors, genetic and environmental.

The action of genes solely determines both ABO blood type and haemophilia and no environmental factors are involved. Conversely, diseases such as cholera and AIDS can affect anyone, regardless of their genetic makeup. Asthma, however, is an example of a disease thought to have a genetic basis, but which requires certain environmental factors such as climatic conditions and pollens for induction.

Likewise, the sizes and shapes of teeth and different degrees of susceptibility to tooth decay depend on both genetic and environmental factors. Common diseases such as dental caries and periodontal (gum) disease are infectious in nature, because the germ responsible for tooth decay can be transmitted from one person’s mouth to another. However, the problems are often considered to be mainly environmental. But even this being the case, researchers are convinced that the genetic aspects that influence the degree of susceptibility should not be overlooked.

The basic element in genetics is in the gene. It is found in the nucleus of every cell. A body containing many genes is a chromosome. Humans have 46 chromosomes in each cell. Chromosomes are made in pairs, which closely resemble each other. There are 23 such pairs, of which one concerns sex. One of a set of chromosomes comes from one of either parent. Each of the thousands of genes is responsible for a specific attribute. For example, there is a gene for the colour of the eyes, one for the shape of the nose, one for the colour of the skin, etc. Environmental factors may alter the composition of genes, which, when it occurs, is known as mutation.

Cancer is a classic example of a condition caused by gene mutation which an external agent triggers.
After the alteration occurs in a gene, the change will be transmitted to descendants. That is why certain conditions such as heart disease and diabetes tend to perpetuate in families.

There are many dental and maxillofacial diseases that are mainly transmitted along genetic lines. During the years of my working at the Department of Oral and Maxillo-facial surgery, I can readily cite two common examples; facial keloids (abnormal proliferation of scar tissue) is seen almost exclusively in Afro-Guyanese and cleft lip/palate seen almost exclusively in Indo-Guyanese.

A study, published in the Journal of Periodontology of December 2010, concludes that approximately half of the variants in gum disease in the population can be attributed to genetic differences. There are many genes that play a role in susceptibility, and these may differ in different races and ethnic groups. For example, this author observed that in the village of Paramakatoi, while multiple decayed teeth is very common among that Amerindian community, the prevalence of gum disease is low. So one can say with a fair degree of accuracy that you can blame your oral health status partly on your parents.

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